Electric rotary switch indexing means



Aug. 7, 1962 1.. w. D. SHARP ET AL 3,048,684

ELECTRIC ROTARY SWITCH INDEXING MEANS Filed Dec. 1,1958

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United States Patent 3 048 684 ELECTRIC ROTARY SWITCH INDEXING MEANS Leonard William Descarrieres Sharp, Loughton, and Donnis Jack Blight, Woodford Green, England, assignors to The Plessey Company Limited, London, England, a

British company Filed Dec. 1, 1958, Ser. No. 777,527 Claims priority, application Great Britain Dec. 2, 1957 1 Claim. (Cl. 200-166) This invention relates to electric rotary switches and is particularly applicable to a device for changing circuits, such as for example a wave change switch.

In rotary switches for changing circuits it is customary to have an indexing mechanism to control the rotary movement between the rotary contacts and stator contacts. It has previously been proposed to provide an indexing mechanism consisting of a spring-loaded plate which is fitted with balls; said plate presses the balls against an index plate so that upon rotation of the plate the balls click at predetermined positions into indexing recesses. The device thus provides What is generally known as a clicking device. This construction is not very convenient in manufacture, more particularly in sizes suitable for miniature switches.

An object of this invention is to provide an improved indexing mechanism which is particularly applicable to a miniature rotary switch.

According to the invention a drum carries an indexing ring which is free to slide axially relative to the drum, and a spring is arranged inside the drum which presses said indexing ring against an index plate. The drum is mounted upon a driving shaft to enable the drum to transmit a drive to the index ring.

An advantage of this arrangement is that the drum provides ample space for accommodating the spring; preferably a helical spring with a very low stress level is used.

A feature of the invention is the provision of means for the drum to engage with the indexing ring at maximum radius thereby reducing the effect of any play in the device.

A further feature of the invention is that the drum can be packed with grease or the like with a view to increasing the reliability and the life of the assembly.

Another feature of the invention is the provision of a stop plate for limiting the rotary movement of the drum.

A convenient embodiment of the invention is illustrated in the accompanying drawing in which:

FIGURE 1 is a sectional elevation, and

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FIGURE 2 is an end view of a switch contact assembly and indexing mechanism.

Referring to the drawing:

Side plates 1 support a switch contact assembly 2 having a driving shaft 3.

An index mechanism comprises an open-ended drum 4 which is mounted upon the shaft 3 and is compelled by flats So on the shaft 2 to rotate with the shaft. Two diametrically opposed longitudinal slots 5 are cut in the open end of the drum to accommodate lugs 6 integral with an indexing ring 7. A helical spring 8 of very low stress level is inserted within the drum and around the shaft 3 for pressing said ring 7 against an index plate 9 which in turn is secured to the side plates 1.

A stop plate 10 is fixed to the rear face of the drum 4, and end stops 11 spaced a suitable distance apart are fixed to one end of the switch contact assembly 2 for limiting the movement of rotation of the drum 4 in a clockwise or anti-clockwise direction.

What we claim is:

A combined indexing and drive device for an electric switch, comprising a cup-shaped drum mountable on the drive shaft of the switch, such that the drum is constrained to rotate with the drive shaft, the drum having a base through which the shaft passes and a wall axially directed transversely of the base, an indexing ring located within the drum and free to slide axially of the shaft, an indexing plate located within the drum, the plate having means whereby it can be constrained against rotation with the drum, a spring arranged within the drum, the spring bearing on the base of the drum and serving to press the indexing ring against the indexing plate, a driving connection between the wall of the drum and the indexing ring, the connection between the drum and the ring being at a greater radial distance from the axis of rotation of the shaft than is the distance from the axis at which the ring indexes with the plate.

References Cited in the file of this patent UNITED STATES PATENTS 2,113,463 Hall Apr. 5, 1938 2,519,215 Appleton et al Aug. 15, 1950 2,531,246 Batcheller Nov. 21, 1950 2,679,557 Miller May 25, 1954 2,687,275 Hufi Aug. 24, 1954 2,690,481 Courtney Sept. 28, 1954 2,692,309 Ellithorpe Oct. 19, 1954 

